BIRDS — CYGNINAE, 



757 



Sub-Family CYGNINAE. 

 CYGNUS, Linnaeus. 



Cygnus, Linnaeus, Syst. Nat. 1735. Type Anas olor, Gmelin. (Gray.) 



Ch. — Neck very long. Bill longer than the head, (commissure longer than the tarsus,) the basal portion covered by a soft skin 

 extending to the anterior half of the eye, the plane of the upper outline from eye to eye horizontal ; the lateral outline extending 

 nearly straight to the commissure, or even sometimes widening slightly ; not half the width of the bill at tip. Nostrils situated 

 in the middle portion of the bill. Lower portion of tibia bare ; the tarsus much shorter than the foot, much compressed, covered 

 with hexagonal scales, which become smaller on the sides and behind. Hind toe small, much elevated ; the lobe narrow. Tail 

 of 20 or more feathers, rounded, or wedge-shaped. Sexes similarly colored. 



As North America possesses only one genus of Gygninae, I have combined the suh-family 

 characters with the generic in the preceding diagnosis. By Wagler the peculiarities of the hill 

 have been made the basis of sub-divisions of the old Linnaean genus Oygnus, as follows : 



Cygnus. — Bill with a swollen fleshy tubercle at the base of culmen. Teeth of the edge of 

 bill projecting and visible from the side. 



Olor, Wagler. — No tubercle at the base of bill. Teeth of the edges of bill not projecting. 



Other members of Cygninae are Chenopis, embracing the Australian black swan, and 

 Coscoroba, a South American white species with feathered lores. The black-necked swan of 

 South America belongs to the sub-genus Cygnus. 



There are certain peculiarities of trachea and sternum which distinguish the genus and itg 

 species in a marked degree. 



The two North American species of swan belong to Olor as restricted, with the following 

 diagnoses : 



Tail feathers 20. Bill as long as the head. The anterior end of nostrils considerably beyond 

 the middle of commissure. Black naked skin at base of bill, with a reddish spot anterior to the 

 eye ■ C americanus. 



Tail feathers 24. Bill longer than head. Anterior end of nostril opposite the middle of 

 commissure. Skin at base of bill entirely black C. buccinator. 



Comparative measurements of species. 



